In prior art manufacturing processes of substrate-type thin-film solar cell materials, a back contact or back reflector layer is deposited, then semiconductor layers are deposited, and then the top contact layer is deposited to complete the basic solar cell or photovoltaic (PV) cell structure. The cell is then tested offline to obtain quality control (QC) measurements. In methods available in the art, these processes are carried out in separate machines, which increases capital cost and reduces throughput due to load/unload times. These times can run into hours for large machines. Also, when separate machines are used, an interleaf material must be inserted between wraps of the semiconductor material as it is wound up before transfer to the top-contact machine. Due to the requirements of cleanliness, vacuum compatibility and temperature resistance, these interleaf materials can be expensive.
Advances in better understanding of hydrogenated amorphous silicon (a-Si:H) materials and devices have led the a-Si:H based solar cell R&D results into large-area a-Si:H based PV module mass production, including substrate-type and superstrate-type processes. A state of art thin-film silicon (tf-Si) based photovoltaic (PV) manufacturing process on stainless steel (SS) web substrate could include a front-end roll-to-roll production line for thin film solar cell material deposition and a back-end production line for PV module assembly. The roll-to-roll method has been described in M. Izu and S. R. Ovshinsky, “Production of Tandem Amorphous Silicon Alloy Cells in a Continuous Roll-To-Roll Process”, SPIE Proc. 407 (1983) 42, and M. Izu, H. C. Ovshinsky, X. Deng, A. J. Krisko, K. L. Narasimhan, R. Crucet, T. Laarman, A. Myatt, and S. R. Ovshinsky, “Continuous Roll-to-roll Serpentine Deposition for High Throughput a-Si PV Manufacturing”, in: IEEE First World Conference on Photovoltaic Energy Conversion, (1994) p 820, all of which are entirely incorporated herein by reference.
Prior art roll-to-roll methods typically require the use of several machines, which increases capital cost and reduces production throughput due to load/unload times, process reproducibility, production yield, machine reliability, machine maintainability. In systems employing a single roll-to-roll machine, problems with cross contamination (i.e., gases from one chamber entering and contaminating an adjacent chamber) lead to poor film qualities, leading to increases in manufacturing costs and decreases in efficiency. Accordingly, there is a need in the art for deposition processes that provide high quality thin films while minimizing production costs.